BAR HARBOR, Maine — With the help of researchers and a photograph at College of the Atlantic, scientists have made a discovery that suggests humpback whales may travel and breed farther afield than previously believed.

By matching an identification photo from the school’s humpback whale catalogs to a photo of a diving humpback that a Norwegian tourist took off the coast of Madagascar, researchers have documented the longest journey for any nonhuman mammal, COA officials said this week.

The photo in the catalog, maintained by COA’s Allied Whale program, was taken off the coast of Brazil, more than 6,000 miles away from the east African island nation.

The matching photos of distinctive markings on the whale’s tail are several years old but the match was made earlier this year by Hancock resident Gale McCullogh, a longtime volunteer associate at Allied Whale. An article about the finding is being published this week in Biology Letters, the scientific journal of the United Kingdom’s Royal Society.

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According to Peter Stevick, an Allied Whale researcher based in Rockport, the female humpback was photographed off Brazil in August 1999 and then off Madagascar in September 2001. The photo taken off Madagascar spent several years sitting in a drawer as a slide before it was scanned and published on the Internet via the photo-sharing site Flickr, he said.

The photos show that humpbacks are capable of traveling between breeding populations that had been thought to be separate and distinct, Stevick said Tuesday.

Whales tend to travel from temperate regions to tropical regions as the seasons change, feeding in cooler waters and breeding in warmer ones, according to Stevick. Because of the alternating seasons in the northern and southern hemispheres, breeding populations that generally are found off the coasts of continents tend to travel north and south along those coasts without making contact with one another.

This assumed genetic isolation has been a concern for scientists who have studied how whale populations have rebounded since most nations stopped commercial hunting of whales in the 1960s. Some breeding populations have recovered significantly, but others have not. Injuries from ship strikes and entanglement in fishing gear continue to affect the populations of humpbacks and other endangered whales, according to researchers.

Stevick, who hopes the finding will lead to greater collaboration between whale research organizations, said there aren’t good estimates for how many humpback whales exist today in the Southern Hemisphere. He said researchers believe 200,000 whales were killed in the Southern Hemisphere in the 20th century, up until such hunting largely stopped about 50 years ago.